Optimize chained string concatenation with counted CONCAT

[bertysentry]

Summary

• Flatten concatenation ASTs so a whole string chain compiles to a single counted CONCAT tuple.
• Update the AVM to concatenate N operands with StringBuilder while preserving left-to-right evaluation order.
• Extend tuple optimization so literal-only counted concatenations fold to one string literal.
• Add JMH benchmarks for constant, mixed, and four-field string concatenation cases.
• Add regression tests for counted concat generation and literal-folding behavior.

Testing

• mvn test
• mvn verify
• mvn -Pbenchmark -DskipTests package

[chatgpt-codex-connector]

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[Copilot]

Pull request overview

This PR optimizes AWK string concatenation by compiling chained concatenations into a single counted CONCAT tuple, updating the AVM to concatenate N operands efficiently, and extending tuple peephole optimization to fold literal-only counted concatenations into a single string literal. It also adds regression tests and expands JMH benchmarks around concatenation scenarios.

Changes:

• Flatten concat ASTs to emit a single counted CONCAT(N) tuple for a concatenation chain.
• Update AVM CONCAT execution to concatenate N operands using a pre-sized StringBuilder.
• Add tuple optimization + tests for folding counted literal-only concatenations, plus additional JMH benchmark cases.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/test/java/io/jawk/AwkTupleOptimizationTest.java	Adds regression tests for counted concat emission and literal-folding behavior.
src/main/java/io/jawk/intermediate/Opcode.java	Updates CONCAT opcode documentation to describe counted semantics.
src/main/java/io/jawk/intermediate/AwkTuples.java	Adds counted concat(int) emission and folds counted literal-only string concatenations.
src/main/java/io/jawk/frontend/AwkParser.java	Flattens concat ASTs to generate a single counted concat tuple.
src/main/java/io/jawk/backend/AVM.java	Implements counted CONCAT(N) runtime concatenation using StringBuilder.
src/jmh/java/io/jawk/backend/AVMExpressionBenchmark.java	Adds new concatenation-related JMH benchmarks.

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated no new comments.